You are expected to follow the Southern Dress Code while visible to faculty or students on Zoom or other online venues. Remember that, even though you may be alone at home, your professor and classmates can SEE you!
Be aware of your surroundings. Your professor and classmates can also see BEHIND you. Make sure that there is nothing in the background (traffic, other people, a pile of laundry) that may distract from the class. While it is not necessarily the best choice to attend class from your messy bedroom, it may be the only place you can find peace and quiet away from roommates or family members. If that is the case, you can employ a Virtual Background to hide what you don't want seen.
Mute is your friend. Once you log in to the virtual classroom, be sure to mute your microphone (lower left-hand corner). This will help to eliminate background noise that could distract others.
Raise your hand and wait to be called upon. If you wish to speak, either physically raise your hand or use the "Raise Hand" button at the center of the bottom of your screen. Once the teacher calls on you, unmute yourself and begin speaking. When you have finished speaking, indicate you are done by saying something like "That's all" or "Thank you" and then mute your microphone again. This may change from class to class, so consult your teacher on this policy.
If you don't have anything nice to say... The Zoom chat feature is a tool to make comments and ask questions without interrupting the speaker but be aware that your comments are public and are recorded in the minutes of the session. As you most likely learned in your first face-to-face classroom back in kindergarten, "If you don't have anything nice to say, ...don't say anything at all."